Window and passive interference generator



Oct. 29, 1963 F. H. NUMRlcH wINnow AND PAssIvE INTERFERENCE GENERATOR 2 Sheets-Sheet 1 Filed Dec. 18, 1961 MWIQQW bolm. WTAK mumrm Oct. 29, 1963 F. H. NUMRlcH 3,109,045

wINnow AND PAssIvE INTERFERENCE GENERATOR med 1180.118, 1961 2 sheets-sheet 2 s'mGE coNTAl/vllva wmoow oeoP Farmen WINDOW DROP KAND PASS/VE Y INTERFEIZENCE VDEO PAS S l VE IN TERFEIZENGE SL IDE AZ IMU TH ANGLE 10 cA'rHoDE RAY 'rues RADAR 70m-I Die! VE ANTENNA- ssvo Ro'm'ruve yoke: AzlMu'rH oop I 2o ZZ f? f 2 INVENTOR FEED H. NUMRICH United States Patent (D 3,109,046 WiNDW AND PASSVE RNTERFERENQE GENERATR Fred H. Numrich, Wayne, NJ., assigner, by rnesne assignments, to the United States of America as represented by the Secretary oi the Navy Filed Dec. 1S, 1961, Ser. No. 160,377 8 Claims. (Cl. 35-10 4) This invention relates to an apparatus tor simulating Window drop interference. Window drop interference is generated during actual tactical oper-ation by the release of metallic material from an aircraft target. A metallic material re-radiates R.F. energy causing a video indica-tion on operational radar indicators that has no definite form but which increases in size with time. Passive interference is caused by return to a radar set due to terrain yor return `due to atmospheric conditions. The function of the window and passive interference generator is to generate video signals that when ted through operational radars appear on respective indicators as typical passive and window interference patterns. Previously utilized methods for simulating window drop interference and passive interference relied upon prepared 'overlays which had a particular random pattern previously `drawn thereupon. This prepared overlay was then projected upon a radar display thereby simulating window drop and passive interference. lHowever,'such a previously prepared pattern did not accurately simulate random window drop interference and passive interference. `ln addition, its usefulness for training purposes for training purposes was limited4 in that its' pattern would become recognizable to trainees and it would not appear random after more than a single use.

An object of the present invention is `to provide a novel window drop and passive interference generator.

A further object of the instant invention is to provide a simulation device for simulating a combination of -Window drop and passive interference.

Another object of the instant invention is to provid a novel simulation device lfor generating composite radar displays.

Still another object of the instant invention is to provide a novel device for simulating window drop interference having completely random characteristics.

`Other objects and many `of the attendant advantages of this invention will be readily appreciated as the Same becomes better understood by reference to the following detailed description when considered in connection With the accompanying drawings wherein:

FIG. 1 is a block 'functional diagram of the Window and passive interference generator; and

FIG. 2 is a diagram of `th-e method for defining range and azimuth of passive interference components.

Window drop interference is generated by a moving radar target when it is desired to confuse a tracking or observing radar and thereby obscure its own radar echo. Such interference may be generated by a yfor-m `of an interference screen to obscure the passage of many aircrafts or radar tangets, This interference screen or Window drop, compri-ses pieces of lightweight metal "which are highly refiective and which reilect impinging radar signals in such a pattern so as to provide very strong echoes which have -a random appearance. These very strong echoes tend lto obscure weaker target signals or target echoes.

Referring now to FIG. l, the light from the cathode ray tube iii is used as a scanner. The light from the cathode ray tube sweep is converted into video signals by a photo pickup tube ,l2 after modulation by a passive inter-ference transparency ld and a translucent stage 16 lddtih Patented Oct. 29, 1963 ICC containing a window drop pattern generated by ink drop. Due to the fact that the axis of the passive interference is centered with respect to that of the PPI, each passive interference component of a -given range is converted into a video signal at Ia time required `for the PPI sweep to travel from the Vcenter of the screen to an equivalent point on the transparency. This action can be visualized with the aid of FIG. 2. Thus, referring to the ligure, the axis 1S passes lthrough the passive interference slide l@ and the center of the cathode ray tube scanner lill. lf the sweep of the -PPi which is controlled by the rotating yoke 20 and yoke servo loop 22, is made to rotate in synchronisrn with the operational antenna of the simulator, this operational antenna not being shown, but being present in the operational equipment `or simulation equipment, interference video is generated when respective passive interference components are at the same azimuth Vat an arbitrary time and that unlike passive interference it increases in size with respect to time.

The method utilized to provide such window drop simulation is as follows: A particular target is chosen and its particular slant range voltage `for the target is applied at point 2d to pen drive servo loop 26. This AC. slant range voltage displaces the pen 28 radially above the center `of the paper carrier assembly a Idistance proportional to the range of the simulated aircraft target. lDisplacement of the pen yfrom a given range is kept proportional to sweep speed. This is accomplished by controlling the lpen drive servo loop rate of drive. The azimuth of the window drop is made to follow that of a selected target by supplying the azimuth drive servo loop 3@ with a target azirnuth signal. The azimuth drive servo loop 30 rotates the pen carrier assembly i6 to an angular position that represents the instantaneous azimuth of the simulated aircraft target. Thus, when a window drop impression is initiated, the pen will deposit ink at a rate determined by an external control 32. The pen drive servo loop Z6 will drive the pen to a range position determined by an external signal 24 and Window drop interference video will be developed on the window drop paper assembly ld which has a highly absorbent paper 36 positioned thereon and ink drop pen 28 is driven in an anguiar `direction by azimuth drive servo loop 3d. The photo tubes 3d will then pick up this Window drop simulation ink blot pattern and apply it to the video pickup amplilier i2 which will generate signals representing Window drop with respect to instantaneous range and azimuth of a selected target. The application of ink from the pen 2S is controlled by solenoids which are externally controlled. The ink fonms a spreading ink drop on absorbent paper 36 which is contained on each paper carrier assembly i5. This paper is stored on a roll which is mounted underneath the rcarrier assembly i6. The spread of ink causes the simulation `of window drop video presentation that increases in size with respect to time. Both passive interference, generated by passive interference slide i4, and Window drop inter-ference may be generated simultaneously. A conversion of the passive interference simulation and the Window drop interference simulation to -video signals is accomplished by the multiplier tube 34. A three-stage video amplier l2 is used to raise the level of the passive and window interference video signals before addition to target video on an 11F. modulator section of the simulation device.

iObviously many modifications and variations of the present invention are possible in the light lof the above teachings. It is ytherefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A simulating device for simulating the appearance of window drop and passive interference comprising cathode ray tube scanning means providing a PPI scan, first screen means optically aligned with said scanning means, said first screen means having passive interference opaque areas drawn thereon, and second screen means optically aligned with said rst screen means and said scanning means, said second screen means having window drop generating -means operatively connected therewith for generation of Window drop interference, and phototube pickup means optically operative with said iirst and second screen means and said scanning means whereby said scanning means in conjunction with said first and second screen means and said window drop generating means provide said phototube means with visual simulation of passive and window drop interference, video amplifier means, said video amplifier means connected to the output of said phototube means `for generation of video signals in accordance with the appearance of said passive and window drop interference, an azimuth drive servo loop operatively connected to said second screen :assembly for rotating said second screen assembly in accordance with target azimuth and information signals which are supplied from an external target coordinate generator.

2. The combination of claim 1 and a pen drive servo loop operatively connected to said window drop interference generating means for moving said window drop generating means in accordance with a target slant range signal generated by an external target coordinate 4generator.

3. the structure of claim 2 wherein said window drop generating means comprise a pen holder, a pen and a supply of ink, said pen holder operatively connected to hold said pen, and said ink supply operatively connected to said pen for supplying ink thereto.

4. The combination of claim 3 and control means operatively connected to said pen means for controlling the operation of said pen means and the operation of said ink supply in accordance with an external manual control means.

5. A simulating device `for simulating the appearance of window drop passive interference comprising cathode ray tube scanning means providing a PPI scan, rst screen means optically aligned with said scanning means, said first screen means having passive interference opaque areas drawn thereon, and second screen means optically aligned with said first screen means and said scanning means, said second screen means having window drop generating means operatively connected therewith for generation of window drop interference, phototube pickup means, said phototube pickup means being optically operative with said rst and second screen means and said scanning means whereby said scanning means in conjunction W-ith said first and second screen means and said window drop generating means provide said phototube means with visual simulation of passive and window drop interference, video amplifier means, said video amplifier means being operatively connected to the output of said phototube means for generation of video signals in accordance with the appearance of said passive and window drop interference, a pen drive sewo loop operatively connected to said window drop interference rgenerating means for moving said window drop generating lmeans in accordance with a target sl-ant range sign-al generated by an external target coordinate generator, said window drop generating means comprising -a pen holder, a pen and `a supply of ink, said pen holder operatively `connected to hold said pen, and said ink supply operatively connected to said pen for supplying ink thereto, control means operatively connected to said pen means for controlling the operation of said pen means and the operation of said ink supply in accordance with an extern-al manual control means, said second screen means comprising paper holder means and absorbent paper means whereby said pen means supply ink to the surface of said blotting paper means for generation of opaque ink blots which increase with time in simulation of window drop interference.

6. The structure of claim 5 and high volta-ge supply and sweep amplifier means, said voltage lsupply 'and sweep amplifier means being operatively connected to said cathode ray tube scanning means for providing operating high voltage, sweep voltage, focus voltage, and iblanking voltage, each of said voltages being synchronized with external synchronizing circuits.

7. The combination of claim 6 and yoke means operatively connected to said cathode ray tufbe sweep scanning means and a yol-:e drive servo loop operatively connected to said yoke means for operating said yoke means in accordance with external signals for simulation of antenna scan.

8. The combination of claim 7 and variarble drive means operatively connected to said first screen means for driving said screen means to provide different passive interference patterns.

References Cited in the file of this patent UNITED STATES PATENTS 2,737,730 Spencer Mar. 13, 1956 2,932,093 Lang Apr. l2, 1960 FOREIGN PATENTS 1,022,474 Germany Jan. 9, 1958 

1. A SIMULATING DEVICE FOR SIMULATING THE APPEARANCE OF WINDOW DROP AND PASSIVE INTERFERENCE COMPRISING CATHODE RAY TUBE SCANNING MEANS PROVIDING A PPI SCAN, FIRST SCREEN MEANS OPTICALLY ALIGNED WITH SAID SCANNING MEANS, SAID FIRST SCREEN MEANS HAVING PASSIVE INTERFERENCE OPAQUE AREAS DRAWN THEREON, AND SECOND SCREEN MEANS OPTICALLY ALIGNED WITH SAID FIRST SCREEN MEANS AND SAID SCANNING MEANS, SAID SECOND SCREEN MEANS HAVING WINDOW DROP GENERATING MEANS OPERATIVELY CONNECTED THEREWITH FOR GENERATION OF WINDOW DROP INTERFERENCE, AND PHOTOTUBE PICKUP MEANS OPTICALLY OPERATIVE WITH SAID FIRST AND SECOND SCREEN MEANS AND SAID SCANNING MEANS WHEREBY SAID SCANNING MEANS IN CONJUNCTION WITH SAID FIRST AND SECOND SCREEN MEANS AND SAID WINDOW DROP GENERATING MEANS PROVIDE SAID PHOTOTUBE MEANS WITH VISUAL SIMULATION OF PASSIVE AND WINDOW DROP INTERFERENCE, VIDEO AMPLIFIER MEANS, SAID VIDEO AMPLIFIER MEANS CONNECTED TO THE OUTPUT OF SAID PHOTOTUBE MEANS FOR GENERATION OF VIDEO SIGNALS IN ACCORDANCE WITH THE APPEARANCE OF SAID PASSIVE AND WINDOW DROP INTERFERENCE, AN AZIMUTH DRIVE SERVO LOOP OPERATIVELY CONNECTED TO SAID SECOND SCREEN ASSEMBLY FOR ROTATING SAID SECOND SCREEN ASSEMBLY IN ACCORDANCE WITH TARGET AZIMUTH AND INFORMATION SIGNALS WHICH ARE SUPPLIED FROM AN EXTERNAL TARGET COORDINATE GENERATOR. 